Expandable vertebral prosthesis

ABSTRACT

The present invention relates to an expandable prosthetic implant device for engagement between vertebrae generally comprising an inner member, outer member, gear member and a locking assembly positioned coaxial with respect to each other such that the inner and outer members are moveable relative to each other along an axis. The gear member is axially fixed to the outer member and freely rotatable with respect to the outer member and the gear member threadedly engages a threaded portion of the inner member to translate inner member along the axis. The implant is configured to engage the vertebrae in a predetermined alignment and the gear member includes gear teeth exposed to the exterior and configured to be accessible by a tool member at a plurality of angular positions around the perimeter of the implant device.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 14/157,107, filed Jan. 16, 2014, which is adivisional application of U.S. patent application Ser. No. 12/352,163,filed on Jan. 12, 2009, now U.S. Pat. No. 8,721,723, which isincorporated in its entirety herein.

FIELD OF THE INVENTION

The present invention relates to a device to support the spine afterremoval of at least a part of a vertebra.

BACKGROUND OF THE INVENTION

When a vertebra is damaged or diseased, surgery may be used to replacethe vertebra or a portion thereof with a prosthetic device to restorespinal column support. For example, vertebral body replacement iscommonly required in the treatment of vertebral fracture, tumor, orinfection.

In recent years, several artificial materials and implants have beendeveloped to replace the vertebral body, such as, for example, titaniumcages, ceramic, ceramic/glass, plastic or PEEK, and carbon fiberspacers. Recently, various expandable prosthetics or expandable cageshave been developed and used for vertebral body replacement. Theexpandable prosthetic devices are generally adjustable to the size ofthe cavity created by a corpectomy procedure and typically are at leastpartially hollow to accommodate bone cement or bone fragments tofacilitate fusion in vivo. Some expandable prosthesis may be adjustedprior to insertion into the cavity, while others may be adjusted insitu. One advantage of the vertebral body replacement using anexpandable prosthetic device that is adjustable in situ is that it iseasy to place or insert because it permits an optimal, tight fit andcorrection of the deformity by in vivo expansion of the device. Someother advantages offered by an expandable prosthetic device are thatthey can facilitate distraction across the resected vertebral defect forcorrection of the deformity, and allow immediate load bearing aftercorpectomy.

Instrumentation and specialized tools for insertion of a vertebralimplant is one important design parameter to consider when designing avertebral prosthesis. Spinal surgery procedures can present severalchallenges because of the small clearances around the prosthetic when itis being inserted into position. Another important design considerationincludes the ability of the device to accommodate various surgicalapproaches for insertion of the vertebral implant.

SUMMARY OF THE INVENTION

The present invention relates to an expandable prosthetic implant devicefor engagement between vertebrae generally comprising an inner member,outer member, and gear member positioned coaxial with respect to eachother such that the inner and outer members are moveable relative toeach other along an axis. The inner member has a hollow interior portionand a threaded external portion and includes a first end portionconfigured to engage a first vertebral body. The outer member has ahollow interior portion configured to receive the inner member andincludes a second end portion configured to engage a second vertebralbody. The gear member is axially fixed to the outer member and freelyrotatable with respect to the outer member and the gear memberthreadedly engages the threaded portion of the inner member.

The implant is configured to engage the vertebrae such that first andsecond end portions are oriented in a predetermined alignment withrespect to the first and second vertebral bodies. The gear memberincludes gear teeth extending around the perimeter of the gear memberand the gear teeth are exposed to the exterior and configured to beaccessible by a tool member at a plurality of angular positions aroundthe perimeter.

In one embodiment, the outer member includes a plurality of toollocation holes for receiving a portion of a tool member therein tofacilitate insertion, alignment and engagement of the tool member withthe gear teeth. In another variation, the outer member includes aresiliently deformable portion for receiving the gear member thereon. Inyet another embodiment, the inner member, outer member, and gear membermay be made of a PEEK plastic material. In another embodiment, thedevice also includes a locking member for fixing the inner member withrespect to the outer member.

In one embodiment, the inner member is rotationally fixed with respectto the outer member. In one variation, the inner member includes a slotand a pin extends radially inward from the outer member to engage theslot to prevent rotational movement of the inner member with respect tothe outer member.

In another embodiment, the first end portion may comprise a first platehaving a generally oblong shape when viewed perpendicular to thelongitudinal axis, the first plate extending a width distance along along axis and a depth distance along a short axis, wherein the widthdistance is larger than the depth distance. Similarly, in anotherembodiment, the second end portion may comprise a second plate having agenerally oblong shape when viewed perpendicular to the longitudinalaxis, the second plate extending a width distance along a long axis anda depth distance along a short axis, wherein the width distance islarger than the depth distance. In one variation, the first and secondend plates include at least one bone engaging member extendinglongitudinally from the end plates. The bone engaging members maycomprise metal spikes.

In another variation, end portions have a thickness in the longitudinaldirection and the thickness is variable in the anterior-posteriordirection along the short axis. In one embodiment, the thickness variesgradually in the anterior-posterior direction such that the end portiondefines a general wedge-shaped profile. In another embodiment, the endportion extends in the anterior-posterior direction from an anteriorside to a posterior side and the first end portion has a first thicknessat an anterior side and a second thickness at a posterior side, whereinthe first thickness is greater than the second thickness. In yet anotherembodiment, the end portion includes a bone engaging surface and a planetangent to the bone engaging surface intersects a plane normal to thelongitudinal axis at a first angle. In one variation, the angle isbetween about −16 degrees and about 16 degrees.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more readily understood with reference to theembodiments thereof illustrated in the attached drawing figures, inwhich:

FIG. 1 is a perspective view of a prosthetic device in accordance withan embodiment of the invention;

FIG. 2 is an exploded view of the prosthetic device of FIG. 1;

FIG. 3 is a cross-sectional view of the prosthetic device of FIG. 1taken along line 3-3 of FIG. 1;

FIG. 4 is perspective view of an embodiment of an inner member of theprosthetic device of FIG. 1;

FIG. 5 is perspective view of an embodiment of an outer member of theprosthetic device of FIG. 1;

FIG. 6 is an end view of the prosthetic device of FIG. 1;

FIG. 7 is an elevated side view of one embodiment of a gear member ofthe prosthetic device of FIG. 1;

FIG. 8 is an end view of the gear member of FIG. 7;

FIG. 9 is a cross-sectional view of the gear member of FIGS. 7 and 8taken along line 9-9 of FIG.8;

FIG. 10 is a perspective of one embodiment of a tool according to thepresent invention;

FIG. 11 is a perspective view of the tool of FIG. 10 shown engaging anembodiment of an expandable prosthetic device according to theinvention;

FIG. 12 is a partial cross-sectional view of the combination of FIG. 11;

FIG. 13 is a cross-sectional view of another embodiment of an outermember according to the invention;

FIGS. 14-25 depict various alternate embodiments of expandableprosthetic devices according to the present invention;

FIG. 26 is a perspective view of one embodiment of another toolconstructed according to the invention;

FIG. 27 is an enlarged view of a portion of the tool of FIG. 26;

FIG. 28 is a perspective view of one embodiment of an assembly of thetool of FIG. 26 with one embodiment of an expandable prosthetic deviceaccording to the invention;

FIG. 29 is an enlarged view of a portion of the assembly of FIG. 28;

FIG. 30 is a perspective view of another embodiment of a tool accordingto the invention;

FIG. 31 is a perspective view of another embodiment of a tool accordingto the invention;

FIG. 32 is a perspective view of the tool of FIG. 31 shown adjacent aportion of a spine;

FIG. 33 is a perspective view of another embodiment of an expandableprosthetic device according to the invention;

FIG. 34 is a side view of another embodiment of an expandable prostheticdevice according to the invention;

FIG. 35 is a partial cross-sectional view of another embodiment of anexpandable prosthetic device according to the invention;

FIG. 36 is a partial perspective view of another embodiment of anexpandable prosthetic device according to the invention;

FIG. 37 is a partial side view of another embodiment of an expandableprosthetic device according to the invention;

FIG. 38 is a perspective view of another embodiment of an expandableprosthetic device according to the invention;

FIG. 39 is a cross-sectional view of another embodiment of an expandableprosthetic device according to the invention;

FIG. 40 is a cross-sectional view of another embodiment of an expandableprosthetic device according to the invention;

FIGS. 41-44 are partial cross-sectional views of additional embodimentsof endplate connection mechanisms for expandable prosthetic devicesaccording to the invention;

FIG. 45 is a perspective view of another embodiment of an expandableprosthetic device according to the invention; and

FIG. 46 is an end view of and endplate of another embodiment of anexpandable prosthetic device according to the invention.

FIGS. 47-52 illustrate the locking assemblies according to the presentinvention.

Throughout the drawing figures, it should be understood that likenumerals refer to like features and structures.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention will now be described. The followingdetailed description of the invention is not intended to be illustrativeof all embodiments. In describing embodiments of the present invention,specific terminology is employed for the sake of clarity. However, theinvention is not intended to be limited to the specific terminology soselected. It is to be understood that each specific element includes alltechnical equivalents that operate in a similar manner to accomplish asimilar purpose.

Referring to FIGS. 1-9, one embodiment of an expandable vertebralprosthetic device 10 is shown. Prosthesis 10 generally comprises aninner member 12 which may be telescopingly received within an outermember 14. The prosthesis 10 further comprises a gear member 16generally configured to effect translation of inner member 12 withrespect to outer member 14 and cause expansion of prosthesis 10. Innermember 12, outer member 14, and gear member 16 are centered along alongitudinal axis 18 and define a hollow interior portion which may befilled with bone material, bone growth factors, bone morphogenicproteins, or other materials for encouraging bone growth, blood vesselgrowth or growth of other tissue through the many apertures in thedevice. In one embodiment, members 12, 14, and 16 are made of apolyether ether ketone (PEEK) plastic material. Several known advantagesof PEEK plastic material include that it is radiolucent and may be moreeasily sterilized than other plastics. In alternate embodiments, members12, 14, and 16 may be made of a biologically inert metal alloy or othersuitable materials.

Referring to FIGS. 1-4, inner member 12 has an endplate 20 at a distalend 22 connected to a generally cylindrical body 24 at a proximal end 26and generally defines a hollow interior portion extending axiallytherethrough. Body 24 of inner member 12 generally comprises a wall 27with an inner surface 28 and an outer surface 30 and at least part ofouter surface 30 includes external threads 32. Outer diameter 34 of body24 is dimensioned to be cooperatively received within outer member 14.

Outer member 14 has an endplate 40 at a proximal end 42 connected to agenerally cylindrical body 44 at a distal end 46 and generally defines ahollow interior portion extending axially therethrough. Body 44 of outermember 14 generally comprises a wall 47 with an inner surface 48 and anouter surface 50. Inner diameter 52 of body 44 is dimensioned tocooperatively receive body 24 of inner member 12 within outer member 14.In this regard, inner diameter 52 of body 44 is greater than outerdiameter 34 of body 24 of inner member 12. As shown in FIG. 1, outermember 14 may include one or more openings 53 to permit bone ingrowth.According to one embodiment, a lip 54 is formed around the exterior ofthe distal end 46 of body 44 and is configured to cooperatively fit witha portion of gear member 16. A plurality of relief spaces or slots 56extending through wall 47 are angularly spaced around body 44 adjacentdistal end 46 to facilitate a snapping engagement of lip 54 with gearmember 16. In this regard, slots 56 allow distal end 46 to deformslightly and contract in the radial direction to accommodate gear member16 to snap on to lip 54.

As best seen in FIGS. 2-4, in one embodiment of a prosthetic device 10,inner member 12 includes a plurality of longitudinal slots 36 extendingradially through wall 27. Slots 36 are angularly spaced around body 24and extend longitudinally along wall 27. When inner member 12 isassembled within outer member 14, slots 36 are configured to engage atleast one pin 38 protruding radially inward from the inner surface 48 ofouter member 14 to prevent rotational movement of inner member 12 withrespect to outer member 14. In this regard, pin 38 may extend into oneof slots 36 and may ride within one of the longitudinal slots 36 duringexpansion of the prosthetic device 10 to prevent rotation of innermember 12 with respect to outer member 14. In addition, pin 38 mayprevent inner member 12 from expanding or translating along axis 18beyond a predetermined distance when pin 38 bottoms out or contacts theproximal end 39 of the slot in which it is engaged.

Referring to FIGS. 7-9, gear member 16 comprises a generally hollow body60 extending from a distal end 61 to a proximal end 63 with a helicalthread 62 along at least part of an inner wall 64 and an array of gearteeth 66 along a portion of the exterior wall 68. Gear member 16 isgenerally configured to rotatably connect to distal end 46 of outermember 14 and internal helical thread 62 is configured to engageexternal threads 32 of inner member 12 to cause translation of innermember 12 with respect to outer member 14. In one embodiment, gearmember 16 includes a cylindrical cutout feature 65 extending around theinner wall 64 to cooperatively receive lip 54 of outer member 14. Inthis regard, gear member 16 may rotate freely with respect to outermember 14 while being retained from longitudinal and lateral movement.In this regard, the aforementioned snap-on feature allows for the designand manufacture of a relatively thin walled outer member 14 tofacilitate the creation of a larger inner diameter of outer gear member16 and inner member 12. As a result, more bone growth stimulatingmaterial may be packed into the prosthetic device 10. Also, by creatinga larger inner diameter of gear member 16 and inner member 12, a largerthread size for external thread 32 and internal thread 62 may beutilized to provide greater mechanical strength.

Referring to FIG. 7, gear teeth 66 are positioned at an angle withrespect to the proximal end 63 and extend around the entire periphery ofa portion of exterior wall 68 to form a general frusto-conical gearteeth surface adjacent the proximal end 63. The outer-most externaldiameter 67 of gear member 16 is sized to be the same as or slightlysmaller than the smallest outer diameter of endplates 20, 40. In thisregard, when prosthetic device 10 is viewed from the end in a planeperpendicular to longitudinal axis 18, as shown in FIG. 6, gear member16 does not protrude radially outward from beyond the perimeter ofendplates 20, 40. In one embodiment, the outer-most diameter of gearmember 16 is substantially the same size as the smallest outer diameterof endplates 20, 40. As shown in FIG. 7, in one embodiment gear teeth 66extend a width 69 in a generally radial direction and generally extendradially outward to the outer diameter of gear member 16. In thisregard, teeth 66 may be designed to have a width 69 to accommodate theexpected gear forces given the particular bevel gear ratio, types ofmaterial used, and desired overall inner diameter of prosthetic device10. One skilled in the art will appreciate that the larger the outerdiameter to which teeth 66 radially extend, the larger that teeth 66 maybe designed while still maintaining the same gear ratio. In this regard,when teeth 66 are made larger, they generally have a better mechanicalstrength. Also, the ability to design larger, wider, and stronger teeth66 is advantageous for embodiments wherein prosthesis 10 is made ofPEEK, other plastic, or other non-metallic materials that may have lessmechanical strength than, for instance, titanium. Furthermore, asdescribed in one embodiment, because the outer-most diameter of gearmember 16 may be as large as the smallest outer diameter of endplates20, 40, and teeth 66 extend radially to the outer-most diameter of gearmember 16, a larger inner diameter of gear member 16 may be manufacturedwithout compromising mechanical gear strength. As a result, a largeroverall inner diameter of prosthetic device 10 may be accommodated whichallows the packing of more bone material therein and facilitates bonefusion once prosthetic 10 is implanted.

As seen in FIGS.1 and 2, in one embodiment teeth 66 are substantiallyexposed to the exterior of prosthetic device 10. Because teeth 66 areexposed around the periphery, less material is needed to cover up theexposed teeth, which generally makes the prosthetic 10 lighter andeasier to manufacture than prior art devices that require covering thegear teeth. In addition, the gear member 16 is more easily visible by asurgeon and more readily accessible by a rotation tool than devices thathide or cover gear teeth. As discussed in more detail below, such afeature allows, inter alia, a tool to engage teeth 66 at a multitude ofangular positions around the periphery of outer member 14 to provide asurgeon with various surgical options for insertion of prosthetic device10. Furthermore, the snap-on assembly feature of gear member 16 allowsfor the manufacture of thinner walled parts without sacrificingmechanical strength. As a result, prosthesis 10 is able to have a largerinternal diameter which allows more space for bone-packing material.

As shown in FIGS. 10-12, prosthesis 10 may be expanded by a tool 70 thatincludes a bevel gear 72 at its distal end. Tool 70 extends along a toolaxis 74 and in operation tool 70 is configured to engage prostheticdevice 10 such that tool axis 74 is generally perpendicular tolongitudinal axis 18. Bevel gear 72 is configured to engage teeth 66 ofgear member 16 such that when bevel gear 72 is rotated about the axis ofthe tool, gear member 16 of prosthetic 10 is rotated about longitudinalaxis 18 and inner member 12 translates along longitudinal axis 18 toexpand prosthesis 10. In one embodiment, tool 70 may include a centralshaft 76 having a threaded distal tip portion 78 that extends distallybeyond bevel gear 72 to facilitate location and mounting of tool 70 withprosthetic 10. Threaded distal tip portion 78 may be configured toextend radially through a tool location hole 80 in outer member 14 andthreadedly engage a threaded hole 81 located on the inner surface 48 ofwall 47 positioned diametrically opposite hole 80 to fix the centralshaft 76 of tool 70 to outer member 14. Once central shaft 76 is fixedto outer member 14, bevel gear 72 may rotate with respect to centralshaft 76 to effect rotation of gear member 16 and translation of innermember 12.

Referring again to FIGS. 2 and 4, in one embodiment of prosthetic device10 a plurality of mounting features or tool location holes 80, 82, 84are provided along the outer surface 50 of outer member 14. Toollocation holes 80, 82, 84 may be spaced around outer surface 50 in apredetermined arrangement to allow insertion of prosthetic device 10utilizing different surgical approaches. For example, one skilled in theart will appreciate that holes 80, 82, 84 may be arranged to permitinsertion through a lateral approach, anterolateral approach, or ananterior approach. As shown in FIG. 4, tool location hole 80 isangularly located or positioned on wall 47 toward the front ofprosthetic 10 or toward the short end of end plates 20, 40 to facilitateinsertion of prosthetic device 10 into a patient via an anteriorapproach. Tool location hole 82 may be angularly located or positionedon wall 47 to be toward the side of prosthetic 10 or toward the long endof end plates 20, 40 to facilitate insertion of prosthetic device 10into a patient via a lateral approach. In addition, a third toollocation hole 84 may be angularly located or positioned to be betweenlocation holes 80 and 82 to facilitate insertion of prosthetic device 10through an anterolateral approach. As described previously, for eachlocation hole 80, 82, 84, a corresponding threaded hole 81, 83, 85 maybe formed on the inner surface 48 of wall 47 and positioneddiametrically opposite the corresponding tool location hole to permitthe threaded engagement of distal tip portion 78 of tool 70.

As best seen in FIGS. 1, 2 and 4, a locking member 120 may be providedto substantially restrict all relative movement between inner member 12and outer member 14, when, for example, the desired expansion of theprosthetic device 10 has been obtained. In one embodiment of the lockingmember 120 according to the invention, a portion of locking member mayprotrude radially inward from the outer member 14 to engage the externalsurface 30 or thread 32 of inner member 12 and lock or fix inner member12 to outer member 14 by friction and/or deformation of external threads32. An internal locking screw 121 may be provided internal to lockingmember 120 to translate the locking member radially inward when thescrew 121 is rotated. Screw 121 may be provided with a hexagonal head atits externally exposed end to facilitate engagement with an allen wrenchor other tool to rotate screw 121 and drive locking member 120 radiallyinward to lock inner member 12 in place. In one embodiment, a pluralityof locking members 120, 122, 124 may be provided spaced around theperiphery of outer member 14 such that a surgeon can easily extend thelocking member when utilizing any one of the aforementioned toollocation holes 80, 82, 84.

Referring to FIGS. 1-9, one embodiment of end plates 20, 40 is shownwherein each end plate has a generally oblong or elliptical shape whenviewed from the end or perpendicular to the longitudinal axis 18. Asshown in FIG. 6, each end plate 20, 40 generally extends a widthdistance 90 (large outer diameter) along a long axis 92 in amedial-lateral direction and a length distance 94 (small outer diameter)along a short axis 96 in the anterior posterior direction, wherein width90 is larger than the length 94. The oblong or elliptical shape of endplates 20, 40 is designed to resemble or mimic the footprint of thevertebral body to which the end plates will engage. In this regard, endplates 20, 40 are configured to engage portions of the vertebrae in apredetermined orientation, namely with long axis 92 extending in amedial-lateral direction, to maximize contact of the superior surface ofthe end plates 20, 40 with bone.

The dimensions of end plates 20, 40 can be varied to accommodate apatient's anatomy. Typically, end plates 20, 40 may have a width betweenabout 14-32 mm (in the medial-lateral direction) and a length betweenabout 12-25 mm (in the anterior-posterior direction). In someembodiments, implants 20, 40 have a wedge-shaped profile to accommodatethe natural curvature of the spine. For example, as shown in FIG. 13,one embodiment of a wedge shape is shown wherein the end plate 130 has agradual decrease in height from an anterior side 132 to a posterior side134. In anatomical terms, the natural curvature of the lumbar spine isreferred to as lordosis. When prosthetic device 10 is to be used in thelumbar region, the angle 136 formed by the wedge should be approximatelybetween 4 degrees and 16 degrees so that the wedge shape is a lordoticshape which mimics the anatomy of the lumbar spine. In alternateembodiments, the wedge shape profile may result from a gradual increasein height from anterior side 132 to posterior side 134 to mimic thenatural curvature in other regions of the spine. Thus, in otherembodiments, angle 136 may be between about −4 degrees and −16 degrees.

As shown in FIGS. 1 and 2, a plurality of mounting holes 98 are spacedaround the perimeter of each end plate 20, 40 for receiving insertablebone engaging members 100. In one embodiment, bone engaging members 100,comprise conical spikes 102 each having a cylindrical base portion 104configured to fit within holes 98, for instance by press-fit. Inalternate embodiments, differently shaped bone engaging members 100 maybe used, or in other embodiments no bone engaging members may be used.Referring again to FIG. 2, according to one embodiment, end plates 20,40 have chamfered edges 106 around the perimeter to facilitate insertionand/or accommodate the shape of the vertebral bodies which they engage.The superior or bone engaging surface 108 of endplates 20, 40 may alsoinclude numerous types of texturing to provide better initial stabilityand/or grasping contact between the end plate and the respectivevertebrae.

The dimensions of prosthetic device 10 in accordance with the inventionmay be as follows, although the dimensions of the embodiments shown inthe figures are not critical to the invention. In one embodiment, innermember 12 may have a total height 140 of between about 13-68 mm, outermember may have a total height 142 of between about 11-64 mm, andprosthetic device 10 may be extended to a total prosthetic height ofbetween about 15-130 mm, depending on the configuration and desiredapplication.

In alternate embodiments, the length, diameter, and shape of prostheticdevice 10 may vary to accommodate different applications, differentprocedures, implantation into different regions of the spine, or size ofvertebral body or bodies being replaced or repaired. For example,prosthetic device 10 may be expandable to a longer distance to replacemultiple vertebral bodies. Also end plates 20, 40 can be sized andshaped to accommodate different procedures. For example, end plates 20,40 may be made smaller for smaller statured patients or for smallerregions of the cervical spine. In addition, it is not required that endplates 20, 40 be shaped and sized identically and in alternateembodiments they can be shaped or sized differently than each otherand/or include different bone engaging members or texturing.

Referring to FIGS. 14-25, various alternate embodiments of expandableprosthetic devices according to the present invention are shown.Referring to FIGS. 14 and 15, in one variation a central gear member 140may be positioned between the inner and outer members to engage teeth142 to facilitate expansion. Referring to FIG. 16, in another embodimentan oblong cam 160 may be used to facilitate expansion. As shown in FIG.17, an eccentric driver 170 may be used to mate with an oblong hole 172to provide expansion. As shown in FIG. 18, in another embodiment analternate worm gear 180 can be used. Referring to FIG. 19, a slot 190with a cam lock 192 may be used to expand and lock the device at acertain expansion distance. Referring to FIGS. 20 and 24, in otherembodiments, a scissor jack 200 and threaded screw 202 may be used tofacilitate expansion. As shown in FIG. 24, a wedge 204 may be used toengage the scissor jack 200. Referring to FIGS. 21 and 22, alternatethreaded devices may be used to expand the prosthetic device. As shownin FIG. 21, a tapered screw 210 may be used that may be driven by adriver 212. Alternatively, as shown in FIG. 22, a simple screw threadedengagement between the inner member and outer member may used. Also aset screw 220 may be used to lock the device at a certain expansiondistance. Referring to FIGS. 23 and 25, the inner and outer members maybe shaped to ride along an inclined plane or ramp. As shown in FIG. 23,a locking wedge or ring 230 may be provided to lock the device at acertain expansion distance. As shown in FIG. 25, rollers 250 may beprovided to facilitate expansion of the device.

Referring to FIGS. 26-27, another embodiment of a holder or tool 260 isshown that may be used to hold, insert, and/or expand a prosthesis ofthe invention. Tool 260 extends along a longitudinal or tool axis 262and includes a bevel gear 264 adjacent its distal end 266. Tool 260comprises arms 268 extending longitudinally along axis 262 and defininga claw or clamping portion 270 adjacent distal end 266. As describedabove with respect to tool 70, bevel gear 264 is configured to engageteeth 66 of gear member 16 to expand prosthesis 10. In this embodiment,clamping portions 270 of arms 268 are configured to engage the lateralsides or exterior central portion of prosthesis 10 to clamp and/or holdprosthesis 10 therebetween while allowing bevel gear 264 to rotate andexpand prosthesis 10. As best seen in FIG. 27, in one embodiment,clamping portions 270 may include teeth or bevels 272 configuredgenerally to facilitate or enhance the grip or purchase of a prosthesisbetween the clamping portions 270 of arms 268. As shown in FIG. 26, arms268 may be actuated by compressing proximal ends 274. In this regard, ahinge 282 may be provided intermediate the length of arms 268 whichcauses clamp portions 270 to compress inward when proximal ends 274 ofarms 268 are compressed inwards. In one embodiment, proximal ends 274may be threadedly interconnected and may be actuated by advancing orrotating a screw 276. In operation, the threaded portion of screw 276mechanically aids in the physical clamping or holding force applied onprosthesis 10 by clamping portions 270. One skilled in the art willappreciate that a surgeon's hands may be freed to perform other taskswhile being assured that a secure hold of prosthesis 10 by tool 260.

Bevel gear 264 may be rotated by dial 278 positioned adjacent a proximalend of shaft 280. In this regard, a surgeon may actuate or expandprosthesis 10 remote from the prosthesis, i.e. outside of a patient'sbody during implantation. In one embodiment, centering or positioningpin 284 extends distally from bevel gear 264 and is configured anddimensional to engage an opening in prosthesis to locate bevel gear 264adjacent gear member 16 of prosthetic 10. Referring to FIGS. 28-29,perspective views of tool 260 assembled to a prosthetic 10 are shown.

Referring to FIG. 30, another embodiment of a holder or tool 300 isshown that may be used to hold, insert, and/or expand a prosthesis ofthe invention. According to this embodiment, tool 300 is configured tobe used with prosthesis 10 utilizing a transforaminal approach. In thisregard, tool 300 is configured and dimensional to engage or holdprosthesis 10 at an angle with respect to tool axis 302.

According to one embodiment, tool 300 extends along a longitudinal ortool axis 302 and generally comprises an angled distal end portion 304extending at an angle 306 with respect axis 302. In one embodiment,angle 306 is between about 30 and about 60 degrees. In anotherembodiment, angle 306 is about 45 degrees. Distal tip 308 of end 304 maycomprise prongs 310 extending distally on either side of bevel gear 312.Prongs 310 are configured and dimensioned to engage openings inprosthesis 10 to locate bevel gear 312 adjacent gear member 16 ofprosthetic 10. In this embodiment, prongs 310 may be extendable in thedistal direction from portion 304 to hold or grip prosthetic 10. In onevariation, a compressible handle 314 may be provided to actuate prongs310 in an outward or distal direction to contact, engage, or holdprosthesis 10 at a distal end of tool 300. A flexible shaft 316 mayextend the length of tool 300 from rotation sphere 318 to bevel gear312, such that bevel gear 312 may be rotated upon rotation of sphere318. As with previously described embodiments, a surgeon may actuate orexpand a prosthesis 10 remote from the prosthesis or outside thepatient's body during implantation. Handle 314 may be released to causeprongs 310 to retract and release prosthesis 10 once the prosthesis isimplanted.

Referring to FIGS. 31 and 32, another embodiment of a holder or tool 320is shown. Tool 320 is similar to tool 300 except prongs 310 are notactuatable by a compressible handle, as described above. In thisembodiment, a set screw 322 is provided to threadedly engage prosthesis10 to fixedly hold or secure prosthesis 10 with respect to tool 320.According to one embodiment, tool 320 may also include an alternaterotating mechanism, such as rotating dial 324, to rotate the bevel gear326 positioned at the distal tip of the tool. Referring to FIG. 32, anassembly view of tool 320 with prosthesis 10 attached thereto is shown.As with tool 300, tool 320 is configured and dimensioned to insert,engage, or hold prosthesis 10 at an angle with respect to thelongitudinal axis of the tool and is generally configured to beimplanted using a transforaminal approach, as shown in FIG. 32. Onceimplanted, a surgeon can loosen screw 322 to release prosthesis 10

Referring now to FIG. 33, an alternate embodiment of an expandablevertebral prosthesis device 340 is shown. Prosthesis 340 is generallysimilar to prosthesis 10 with the exception that the endplates 342, 344are rotatably and pivotably connected to the body 346 of prosthesis 340.In this embodiment, endplates 342, 344 are rotatable and/or pivotableabout multiple axes. As such, endplates 342, 344 are multi-axiallyconnected to body 346 of prosthesis 340. In one embodiment, endplates342, 344 are selectably fixable at any desired pivot angle or rotationposition. As with the embodiments disclosed above, prosthesis 340generally comprises an inner member 348 telescopingly received within anouter member 350 and a gear member 352 generally configured to effecttranslation of inner member 348 with respect to outer member 350 andcause expansion of prosthesis 340. A first endplate 342 is connected todistal end 354 of inner member 348 and second endplate 344 is connectedto a proximal end 356 of outer member 350. According to one embodiment,endplates 342, 344 generally comprise a generally flat outer or boneengaging surface 358 and an opposite connecting or articulating portion360. Outer surface 358 is generally configured and dimensioned tocontact or engage a bone surface, such as a portion of a vertebral body.According to one embodiment, articulating portion 360 has a generallyspherical or ball shaped exterior 362 and is configured to articulatewithin or engage a correspondingly shaped socket 364 and facilitatesrotational and/or pivotal articulation or movement therein. According toone embodiment, socket 364 may be defined within a clamping member 366so that endplates 342, 344 may be selectably fixed at any position withrespect to socket 364 when so desired by a user or surgeon. As seen inFIG. 33, in one embodiment, clamping member 366 generally comprises aC-shaped ring or body 368 with an opening 370 extending through aportion of the perimeter to allow the ring or body 368 to contract alongits perimeter and thereby tighten, clamp or otherwise fix thearticulating portion 360 of the endplates in position with respect tosocket 364. In this regard a clamping screw (not shown) may extendacross opening 370 and may be rotated to cause clamping member 366 tocompress or clamp down on articulating portion 360. As one skilled inthe art can appreciate, such a selectable positioning feature ofendplates 342, 344 facilitates the accommodation of a wide variety ofanatomical possibilities when prosthesis 340 is implanted. For example,a surgeon could pivot endplates 342, 344 to accommodate a wide range oflordotic angles of vertebral bodies.

Referring to FIG. 34, an alternative locking mechanism may be providedto selectably lock endplates 342, 344 in place. In one variation,endplates 342,344 may be interconnected to gear member 380 by a cable382 or the like. As ring gear 380 is rotated, a tension is applied oncables 382 pulling end plates 342, 344 closer together to biasarticulating portion 360 against a contact surface of socket 364,thereby preventing further actuation of endplates 342, 344. Referring toFIG. 35, an alternative embodiment of a fixably actuatable endplateattachment mechanism is shown having an alternate locking mechanism.According to this embodiment, articulating portion 392 of endplate 390comprises a spherical socket portion 394 configured to fit, engage orarticulate with respect to a correspondingly shaped ball or sphericalportion 396 to facilitate multi-axial rotation and/or pivotingarticulation of endplate 390 with respect to spherical portion 396 inmuch the same manner described above. A ramped clip or wedge 398 may beinserted into a lateral opening 400 of endplate 390 to effect clamping,locking, or fixation of articulating portion 392 of endplate 390 withrespect to spherical portion 396. In this regard, a collet 402 may beinterposed between socket portion 394 and spherical portion 396 and whenwedge 398 is advanced radially into endplate 390, collet 402 iscompressed downward against socket 394 and spherical portion 396 toprevent further articulation. In one variation, wedge 398 has a partialannular, partial ring, or C-shaped body 404 with a ramped profile whenviewed from the side.

Referring to FIGS. 36-37 additional alternative locking mechanisms areshown for locking or fixing a multi-axial rotatable or pivotableendplate in position with respect to a body of a prosthesis. Referringto FIG. 36, according to one embodiment, an expansion set screw 410 maybe provided to expand a spherical or ball portion 412 of the ball andsocket joint to frictionally engage the socket portion and preventfurther rotation between the ball and socket portions of the joint. Inthis regard, the ball portion 412 may include one or more verticalslits, openings or V-shaped grooves 414 or openings to allow ballportion 412 to expand radially outward when screw 410 is rotated.Referring to FIG. 37 an alternative fixation mechanism is shown whereina tapered collet 420 extends between the ball portion 422 and socketportion 424 and may be advanced or wedged further between the ball andsocket portions to bind the joint and prevent rotation. According to oneembodiment, the collet 420 may be advanced by rotating a cam 426 toadvance a collar 428 and engage the collet 420 and force or wedge collet420 between the ball and socket portions 422, 424 and thereby lock orangularly fix the endplate with respect to the body portion of theprosthesis.

Referring to FIG. 38, another embodiment of an expandable vertebralprosthesis device 430 having at least one fixable multi-axiallyrotatable endplate 432 is shown. Prosthesis 430 is generally similar toprosthesis 340, described above, with the exception that the endplate432 may be fixed in selected angular positions utilizing a pin and skirtmechanism. According to one embodiment, articulating portion 434 ofendplate 432 has a generally conical skirt member 436 defining aspherical socket or female portion 438 configured to engage a sphericalor ball shaped portion 440 provided adjacent an end of prosthesis 430and facilitates multi-axial rotational and/or pivotal movementthereabout. Skirt 436 may comprise a plurality of holes or openings 442spaced about the perimeter of skirt 436 and extending therethrough toaccommodate one or more pins (not shown) to fix or pin skirt 436 andendplate 432 with respect to prosthesis body 444. In this regard, aplurality of corresponding holes or openings (not shown) may be providedabout ball portion 440 to receive one or more pins extending thoughopenings 442 to fix endplate 432 with respect to prosthesis body 444.

Referring to FIG. 39, an alternative embodiment of a prosthesis 450 isshown having an annular endplate 452 with a central opening 454accommodating a partial spherical or ball shaped articulating portion456 on the body 458 of prosthesis 450. A set screw 460 may be providedto clamp endplate 452 with respect to spherical portion 456. The setscrew 460 may extend across a radially extending opening 462 in theperimeter of endplate 452 and generally functions similar to a C-clampas explained above with respect to previously described embodiments.

Referring to FIG. 40 an alternative embodiment of a prosthesis 470 isshown having a pivoting or articulating connection similar to auniversal joint wherein the endplates 472, 474 are pivotable about asingle axis 476. A set screw or other fixation device may be provided ina slotted hinge to facilitate selectable fixation or locking of theendplates at a desired orientation.

FIGS. 41-44 shows various alternative multi-axial coupling mechanismsthat may be used to facilitate fixable angulation and/or rotation ofendplates 342, 344 with respect to a body portion of an expandableprosthesis. Referring to FIG. 41, according to one embodiment, anendplate may be pivotable about a single axis with respect to the bodyof a prosthesis. Referring to FIGS. 42, captured pivotal connections maybe provided to prevent over-rotation of an endplate with respect to thebody of a prosthesis. Similarly, in FIGS. 43-44 locking mechanisms suchas a set screw 480 may be provided to prevent an endplate from rotatingtoo far or over-rotating.

Referring to FIGS. 45 and 46, additional embodiments of expandablevertebral prosthetic devices 490, 500 are shown having endplates withselectable angular orientations. As shown in FIG. 45, prosthesis 490 maycomprise modular insert members 492 having varying angular or wedgeshapes. According to one exemplary embodiment, modular inserts 492 mayhave varying angles from between about 5 degrees to about 30 degrees. Inthis regard, when an angled insert member 492 is interposed into thebody portion 494 of prosthesis 490 a variety of angular orientations ofendplates 496, 498 may be obtained. In operation, a user or surgeoninstalling the prosthetic device may accommodate various lordoticangles. Referring to FIG. 46, in another embodiment, a plurality oftriangular or pie shaped angular inserts 502 may be provided to beinserted directly into an endplate 504 to form the outer surface or boneengaging surface of an endplate. In this regard, a plurality angularinserts 502 may be provided with various angular shapes as desired. Inoperation, a user or surgeon may fashion an endplate having a desiredcontour utilizing any combination of modular angular inserts to, forexample, accommodate a particular lordotic angle when the prosthesis isinserted.

FIGS. 47-52 show a self locking mechanism of the expandable prosthesisaccording to one embodiment of the present invention. FIG. 47illustrates a prosthesis 510 having an upper and lower endplates 512,514, wherein the upper endplate 512 is attached to an inner member 516and the lower endplate 514 is attached to an outer member 518. The innermember 516 is threaded and translatable along the longitudinal axis. Agear member 520 is also illustrated having internal threads that areutilized to translate the inner member 516 along the longitudinal axis.

Now turning to FIG. 48, the gear member 520 is more clearly illustrated.The gear member 520 is provided with a plurality of gear teeth that isadapted to receive the first member of the prosthesis. On the innerportion of the gear member 520, there is provided a plurality of notches522. The notches 522 are dimensioned and configured to receive a lockingmember. The locking mechanism of the present invention will be discussedin greater detail with reference to FIGS. 49-51.

FIG. 49 illustrates a cross-section view of the prosthesis according toparticular one embodiment of the present invention. More specifically,flexible member 524 is shown positioned between the outer member and theinner member of the prosthesis. The flexible member 524 is biased sothat one end of the flexible member 524 is received within one of theplurality of notices of the gear member, as shown in FIG. 50. When theflexible member 524 is engaged with one of the notches 522 of the gearmember, movement of the gear member 520 is blocked thereby blocking anyrelative movement between the inner member 516 and the outer member 518.When an inserter 526 with an insertion point 528 as shown in FIG. 51 isinserted into the outer member 518 of the implant, and the insertionpoint 528 applies pressure on the flexible member 524, and the flexiblemember 524 is moves radially so that the flexible member 524 disengagesfrom the notch and allows the gear member 520 to be rotated. As aresult, the gear member 520 allows relative movement between the innermember 516 and the outer member 518. When the insertion tool 526 isremoved from implant, the flexible member 524 returns to its originalposition and engages with a notch within the gear member 520 andrestricts the gear member 524 from rotating, thereby blocking relativemovement between the inner member 516 and outer member 518.

FIG. 52 illustrates another embodiment of the flexible member 524according the present invention. In this embodiment, the member 524 isprovided with a flexible portion 530 that couples with the anglednotches 522 of the gear member 520. The member 524 may be used as aratcheting device or in the alternative, any type of pressure applyingdevice may be applied on the flexible portion 530 to disengage themember 524 from the angled notches 522.

It should be noted that any type of locking assembly that restricts themotion of the gear member after the implant is positioned is suitable inthe present invention. For example, the locking assembly may utilizeclips, springs, and/or any other type of biased members which can fitinto the notches of the gear member to restrict motion may be used. Itshould also be noted that the notches may be of any general shape andsize that couple with a portion of the flexible member.

While the invention herein disclosed has been described by means ofspecific embodiments and applications thereof, numerous modificationsand variations can be made thereto by those skilled in the art withoutdeparting from the scope of the invention as set forth in the claims.

What is claimed is:
 1. A surgical system comprising: an expandableimplant, the expandable implant comprising: an inner member; an outermember; and a gear member for effecting translation of the inner memberrelative to the outer member, wherein the outer member includes aplurality of tool location holes spaced around an outer surface of theouter member to accommodate insertion of an expansion tool fromdifferent approaches; and an expansion tool configured to be insertedinto any of the tool location holes.
 2. The surgical system of claim 1,wherein the expansion tool comprises a bevel gear for engaging the gearmember.
 3. The surgical system of claim 2, wherein the expansion toolfurther comprises a central shaft extending distally from the bevelgear.
 4. The surgical system of claim 3, wherein the expansion toolfurther comprises a threaded distal tip portion extending distally fromthe central shaft.
 5. The surgical system of claim 1, wherein theexpandable implant comprises at least two tool location holes.
 6. Thesurgical system of claim 1, wherein the expandable implant comprises atleast three tool location holes.
 7. The surgical system of claim 6,wherein each of the at least three tool location holes is positioned ona front wall of the expandable implant.
 8. The surgical system of claim6, wherein the at least three tool location holes permit insertion ofthe expansion tool through a lateral approach, anterolateral approach,or an anterior approach.
 9. The surgical system of claim 1, wherein theinner member is connected to a first endplate and the outer member isconnected to a second endplate.
 10. The surgical system of claim 1,wherein the first endplate comprises a plurality of bone engagingmembers and the second endplate comprises a plurality of bone engagingmember.
 11. A surgical system comprising: an expandable implant, theexpandable implant comprising: an inner member attached to a firstendplate; an outer member attached to a second endplate; and a gearmember for effecting translation of the inner member relative to theouter member, wherein the outer member includes a plurality of toollocation holes spaced around an outer surface of the outer member toaccommodate insertion of an expansion tool from different approaches;and an expansion tool configured to be inserted into any of the toollocation holes.
 12. The surgical system of claim 11, wherein theexpansion tool comprises a bevel gear.
 13. The surgical system of claim12, wherein the expansion tool further comprises a pair of clampingarms.
 14. The surgical system of claim 12, wherein the expansion toolfurther comprises a central shaft positioned distally to the bevel gear.15. The surgical system of claim 14, wherein the expansion tool furthercomprises a threaded distal tip portion extending distally from thecentral shaft.
 16. The surgical system of claim 11, wherein the gearmember comprises an upper portion and a lower portion, wherein the upperportion is toothless and the lower portion includes teeth.
 17. Thesurgical system of claim 11, wherein the first endplate comprises aplurality of bone engaging member and the second endplate comprises aplurality of bone engaging member.
 18. The surgical system of claim 11,wherein the expandable implant comprises at least three tool locationholes.
 19. The surgical system of claim 18, wherein each of the at leastthree tool location holes is positioned on a front wall of theexpandable implant.
 20. The surgical system of claim 18, wherein the atleast three tool location holes permit insertion of the expansion toolthrough a lateral approach, anterolateral approach, or an anteriorapproach.